Mechanical stepper motors

ABSTRACT

A method for stepping a first member relative to a second member. The method including: providing one of the first and second members with one of a plurality of pockets and movable pins offset from each other with a first spacing; providing the other of the first and second members with the other of the plurality of pockets and movable pins offset from each other with a second spacing, where the first spacing is different from the second spacing; and engaging at least one of the movable pins into a corresponding pocket to step one of the first and second members a predetermined linear and/or rotary displacement.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims benefit to U.S. Provisional Application60/958,947 filed Jul. 10, 2007, the entire contents of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to actuators, and moreparticularly to mechanical stepper motor like actuators. The actuatorsare particularly suitable for actuating control surfaces in gun-firedprojectiles, mortars and missiles.

2. Prior Art

Since the introduction of 155 mm guided artillery projectiles in the1980's, numerous methods and devices have been developed for theguidance and control of subsonic and supersonic gun launchedprojectiles. The majority of these devices have been developed based onmissile and aircraft technologies, which are in many cases difficult orimpractical to implement on gun-fired projectiles and mortars. This isparticularly true in the case of actuation devices, where electricmotors of various designs have dominated the guidance and control ofmost guided weaponry.

In almost all guided weaponry, such as rockets, actuation devices andbatteries used to power the same, occupy a considerable amount of theweaponry's internal volume. In recent years, alternative methods ofactuation for flight trajectory correction have been explored, someusing smart (active) materials such as piezoelectric ceramics, activepolymers, electrostrictive materials, magnetostrictive materials orshape memory alloys, and others using various devices developed based onmicroelectromechanical (MEMS) and fluidics technologies.

In general, the available smart (active) materials such as piezoelectricceramics, electrostrictive materials and magnetostrictive materials needto increase their strain capability by at least an order of magnitude inorder to become potential candidates for actuator applications forguidance and control, particularly for gun-fired munitions and mortars.In addition, even if the strain rate problems of currently availableactive materials are solved, their application to gun-fired projectilesand mortars will be very limited due to their very high electricalenergy requirements and the volume of the required electrical andelectronics gear. Shape memory alloys have good strain characteristicsbut their dynamic response characteristics (bandwidth) and constitutivebehaviour need significant improvement before becoming a viablecandidate for actuation devices in general and for munitions inparticular.

The currently available and the recently developed methods and devicesor those known to be under development for guidance and control ofairborne vehicles such as missiles, have not been shown to be suitablefor gun-fired projectiles and mortars. In fact, none have beensuccessfully demonstrated for gun-fired guided munitions, includinggun-fired and mortar rounds. This has generally been the case sincealmost all the available guidance and control devices and methodologiessuffer from one or more of the following major shortcomings forapplication in gun-fired projectiles and mortars:

-   -   1. Limited control authority (generated force or torque) and        high speed actuation capability (dynamic response        characteristics or “bandwidth”), considering the dynamics        characteristics of gun-fired projectiles and mortars.    -   2. Reliance on battery-based power for actuation in most        available technologies and the requirement of a considerable        amount of electrical power for their operation.    -   3. The relatively large volume requirement for the actuators,        batteries and their power electronics.    -   4. The high cost of the existing technologies, which results in        very high-cost rounds, thereby making them impractical for        large-scale fielding.    -   5. Survivability problems of many of the existing devices at        high-g firing accelerations and reliability of operation post        firing, particularly at very high setback accelerations of over        60,000 Gs.    -   6. Relative technical complexities involved in their        implementation in gun-fired projectiles and mortars.

A need therefore exists for actuation technologies that address theserestrictions in a manner that leaves sufficient volume onboard munitionsfor sensors, guidance and control and communications electronics andfuzing as well as the explosive payload to satisfy lethalityrequirements.

Such actuation devices must consider the relatively short flightduration for many of the gun-fired projectiles and mortar rounds, whichleaves a very short time period within which trajectory correction hasto be executed. Such actuation devices must also consider problemsrelated to hardening components for survivability at high firingaccelerations and the harsh environment of firing. Reliability is alsoof much concern since the rounds need to have a shelf life of up to 20years and could generally be stored at temperatures in the range of −65to 165 degrees F.

In addition, for years, munitions developers have struggled withplacement of components, such as sensors, processors, actuation devices,communications elements and the like within a munitions housing andproviding physical interconnections between these components. This taskhas become even more prohibitive considering the current requirements ofmaking gun-fired munitions and mortars smarter and capable of beingguided to their stationary and moving targets, therefore requiring highpower consuming and relatively large electrical motors and batteries. Itis, therefore, important for all guidance and control actuation devices,their electronics and power sources not to significantly add to theexisting problems of integration into the limited projectile volume.

SUMMARY OF THE INVENTION

Accordingly, a mechanical stepper motor is provided. The mechanicalstepper motor comprises: a shuttle having one of a plurality of pocketsand movable pins offset from each other with a first spacing; a bodyportion having the other of the plurality of pockets and movable pinsoffset from each other with a second spacing, where the first spacing isdifferent from the second spacing; and actuation means for engaging atleast one of the movable pins into a corresponding pocket to step one ofthe shuttle and body portion a predetermined linear and/or rotarydisplacement.

The predetermined displacement can be linear. In which case, the bodyportion can comprise a shuttle guide for movably holding the shuttle andpin guides for movably holding the pins.

The predetermined displacement can be rotary. In which case the bodyportion can comprise pin guides for movably holding the pins and theshuttle can be rotatably disposed on the body portion and comprises thepockets.

The activation means can comprise one or more detonation charges forproducing a pressurized gas acting on at least one of the pins to one ofengage and disengage the pins with a pocket. The mechanical steppermotor can further comprise a biasing means for biasing the at least onepin in a disengaged position, wherein the activation means furthercomprises a vent hole for releasing the pressurized gas from acting onthe pin and allowing the biasing means to disengage the at least one pinfrom the pocket. The one or more detonation charges can be provided in aspace in direct communication with a portion of the at least one pin.The one or more detonation charges can be provided to pressurize areservoir in fluid communication with a portion of the at least one pinthrough one or more valves.

The activation means can comprise one or more of the pins having a firstportion acted upon by a first pressurized gas to engage the one or morepins and a second portion acted upon a second pressurized gas todisengage the one or more pins. The first pressurized gas can beprovided by one or more first detonation charges and the secondpressurized gas can be provided by one or more second detonationcharges. The first and second detonation charges can be disposed in thebody.

The activation means can comprise a pressurized fluid source in fluidcommunication with a portion of the at least one pin through one or morevalves. The pressurized fluid source can be one of air and hydraulicfluid.

The mechanical stepper motor can further comprise locking means forlocking a position of one of the shuttle and body relative to the other.

Also provided is a method for stepping a first member relative to asecond member. The method comprising: providing one of the first andsecond members with one of a plurality of pockets and movable pinsoffset from each other with a first spacing; providing the other of thefirst and second members with the other of the plurality of pockets andmovable pins offset from each other with a second spacing, where thefirst spacing is different from the second spacing; and engaging atleast one of the movable pins into a corresponding pocket to step one ofthe first and second members a predetermined linear and/or rotarydisplacement.

The engaging can comprise producing pressurized gas acting on at leastone of the pins to engage the pins with at least one of the pockets. Themethod can further comprise: biasing the at least one pin in adisengaged position; and releasing the pressurized gas from acting onthe pin and allowing the biasing to disengage the at least one pin fromthe pocket. The pressurized gas can be produced in a space in directcommunication with a portion of the at least one pin. The pressurizedgas can be produced to pressurize a reservoir in fluid communicationwith a portion of the at least one pin through one or more valves. Thepressurized gas can be produced to engage the one or more pins and todisengage the one or more pins. The engaging can comprise providing apressurized fluid source in fluid communication with a portion of the atleast one pin through one or more valves.

The method can further comprise locking a position of one of the shuttleand body relative to the other.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the apparatus ofthe present invention will become better understood with regard to thefollowing description, appended claims, and accompanying drawings where:

FIG. 1 a illustrates an overall view of a linear mechanical steppermotor type linear actuator.

FIG. 1 b illustrates a cutaway view of the linear mechanical steppermotor like actuator of FIG. 1 a showing its internal components.

FIG. 2 illustrates a frontal view of the linear mechanical stepper motorlike actuator of FIGS. 1 a and 1 b.

FIG. 3 a illustrates a frontal view of the linear mechanical steppermotor like actuator of FIGS. 1 a and 1 b with the pin C actuated to movethe shuttle one step to the right.

FIG. 3 b illustrates a frontal view of the linear mechanical steppermotor like actuator of FIGS. 1 a and 1 b with the pin B actuated to movethe shuttle one more step to the right.

FIG. 3 c illustrates a frontal view of the linear mechanical steppermotor like actuator of FIGS. 1 a and 1 b with the pin A actuated to movethe shuttle one more step to the right.

FIG. 4 a illustrates an overall view of a rotary mechanical steppermotor like actuator.

FIG. 4 b illustrates a cutaway view of the rotary mechanical steppermotor like actuator of FIG. 4 a.

FIG. 4 c illustrates a close-up view of the cutaway view of the rotarymechanical stepper motor like actuator of FIG. 4 b.

FIG. 5 a illustrates a frontal cutaway view of the linear mechanicalstepper motor like actuator of FIG. 1-3 with double acting actuatingpins.

FIG. 5 b illustrates a variation of a piston for use with the linearmechanical stepper motor of FIG. 5 a shown without the spring.

FIG. 6 a illustrates an overall view of a linear mechanical steppermotor like actuator with a side combined pressurized gas reservoir andgas generating detonation charge unit.

FIG. 6 b illustrates a cut-off view of the linear actuator of FIG. 6 ashowing the pressurized gas chamber and the gas generating charges andother components of the actuator.

FIG. 7 a illustrates an overall view of a linear mechanical steppermotor like actuator with double acting actuating pins and at least onelaterally positioned detonation charges.

FIG. 7 b illustrates a cutaway view of the linear mechanical steppermotor like actuator of with double acting actuating pins and at leastone laterally positioned detonation charges of FIG. 7 a.

FIG. 8 illustrates an overall view of a pneumatic linear mechanicalstepper motor like actuator obtained by replacing the external reservoirunit of the embodiment shown in FIGS. 6 a and 6 b.

FIG. 9 a illustrates a projectile having a canard movable by a rotarymechanical stepper motor.

FIG. 9 b illustrates the projectile of FIG. 9 a having a partialsectional showing the rotary mechanical stepper motor.

FIG. 9 c illustrates an enlarged view of the rotary mechanical steppermotor of FIG. 9 b.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Although the present invention is applicable to numerous types ofactuators, it is particularly useful in the environment of actuators forgun-fired projectiles, mortars and missiles. Therefore, without limitingthe applicability of the present invention to actuators for gun-firedprojectiles, mortars and missiles, it will be described in such anenvironment. Further, the disclosed actuators can also be used anywherea stepper motor (rotary and/or linear) can be used, such as inmanufacturing and inspection processes and robotics. A particular usefulapplication for the disclosed mechanical stepper motors is in linear androtary indexing tables.

The disclosed “mechanical stepper motor” like actuation devices can bedesigned to provide very high force (torque) compared to similar sizedelectrical linear (rotary) motors. The actuators can also be designedwith very high dynamic response characteristics. The high force (torque)and high dynamic response characteristics of the disclosed “mechanicalstepper motor” like actuation devices make them particularly suitablefor gun-fired projectile, mortar and missile guidance and controlapplications. The disclosed actuation technology can be used toconstruct linear as well as rotary actuation devices, particularly thosefor actuating flight control surfaces such as fins and canards ingun-fired projectiles, mortars and missiles. In fact, the disclosedactuation technology can also be used to construct actuation devicespowering devices with arbitrary curved motion paths, including circulararcs.

The actuators disclosed herein require minimal volume since they can bepowered by pressurized gas, such as the detonation of embedded chargesthat could provide high internal pressures and thereby high actuatingforces/torques and high dynamic response, particularly larger than thosepossible by other actuation devices, such as electrical motors. With thedisclosed actuation technology, since solid charges have energydensities that are orders of magnitude higher than the best availablebatteries, a very significant total volume savings is also achieved bythe elimination of batteries that are required to power electricallypowered actuation devices.

It is also noted that the disclosed “mechanical stepper motor” likeactuation devices require minimal electrical power to operate since theyare based on detonation of embedded charges and that charges can bedetonated using as little as 3-5 mJ of electrical energy. It is alsonoted that by significantly reducing the amount of electrical energythat is needed for actuation purposes, it may become possible to utilizeenergy harvesting power sources for their operation, thereby eliminatingthe need for chemical batteries in certain applications.

The disclosed “mechanical stepper motor” like actuation devices arecapable of being embedded into the structure of the projectile, mostlyas load bearing structural components, thereby occupying minimalprojectile volume. In addition, the actuation devices and their relatedcomponents are better protected against high firing acceleration loads,vibration, impact loading, repeated loading and acceleration anddeceleration cycles that can be experienced during transportation andloading operations.

Some of the features of the disclosed “mechanical stepper motor” likeactuation devices for gun-fired projectiles, mortars and missiles andthe like include:

-   -   1. The disclosed actuators can have very high control authority        and very high dynamic response characteristics since they are        based on detonations of charges and utilization of the generated        high detonation pressures to drive the actuation devices. For        example, such a linear actuator operating at a detonation        pressure of around 5,000 psi and with a pressure surface of 0.5        square inches would readily provide a force of around 10,000 N.        A rotary actuator with a similar sized pressure area with an        effective diameter of 2 inches and operating at 5,000 psi could        readily produce a torque of around 250 N-m. In addition,        reliable detonation within time periods of 5-10 msec and even        significantly lower with nanoenergetic materials based ignition        can be readily achievable. This allows motion steps at a rate of        at least 100-200 Hz (cycles per second). For these reasons, the        proposed actuators are particularly well-suited for guidance and        control of precision gun-fired projectiles, mortars and        missiles.    -   2. The disclosed actuators can require very low electrical power        for operation. A large amount of projectile volume is therefore        saved by the elimination of large battery-based power sources        that are required for electrical actuation devices such as        electrical motors and solenoid type actuation devices.        Furthermore, by significantly reducing the power requirement, it        is possible to use onboard energy harvesting power sources and        thereby totally eliminating the need for onboard chemical        batteries. As a result, safety and shelf life of the projectile        is also significantly increased.    -   3. The disclosed actuators can be significantly lighter than        electrical actuation devices that are commonly used for guidance        and control and occupy very small useful volume of the        projectile. This is the case since the disclosed actuators are        high torque/force, fast acting (have high dynamic response        characteristics) and may be integrated into the structure of the        projectile as load bearing structures. The latter characteristic        is also advantageous from the guidance and control point of view        since the actuation force (torque) is applied directly to the        round structure without intermediate components. Almost all such        intermediate coupling mechanisms also introduce flexibility        between the control force (torque) and the projectile structure,        thereby reducing the performance of the feedback control system.    -   4. The disclosed rotary actuators can be designed in an arc form        to provide a desired range of angular rotation. The actuators        may also be designed to provide motion along arbitrarily varying        curved paths without any intermediate cams or other similar        components.    -   5. The disclosed actuators can operate as stepper motors, but        the actuators have the added advantage of being mechanical,        herein referred to as “mechanical stepper motors”, and capable        of being locked following each motion step, and would therefore        require no sensors to close a feedback loop for proper        positioning.    -   6. Due to the capability of the disclosed actuators to be        integrated into the structure of the projectile and their unique        design, they can be readily hardened to survive very high-g        firing loads and very harsh environment of firing. The disclosed        actuators will therefore provide highly reliable devices for use        in gun-fired projectiles, mortars and missiles.    -   7. The disclosed actuators can be built as modular units and can        thereby form the basis for developing a common actuator solution        for almost all gun-fired projectiles, mortars and missiles and        the like for actuating control surfaces and the like.    -   8. The disclosed actuators can be very simple in design, and can        be constructed with very few moving parts and no ball bearings        or other similar joints, thereby making them highly reliable        even following very long storage times of over 20 years.    -   9. The disclosed actuators are scalable to almost any small or        large force/torque requirements.    -   10. The disclosed actuators can be designed to conform to almost        any geometrical shape of the structure of the projectile and the        available space within the projectile housing.    -   11. The disclosed actuators are capable of withstanding high        vibration, impact and repeated loads due to their design        integration into the structure of the projectile.    -   12. The disclosed actuators can be very simple in design and        utilize mostly existing manufacturing processes and components.        As a result, they can provide the means to develop highly        effective but low cost guidance and control systems for guided        gun-fired projectiles, mortars and missiles.    -   13. The disclosed actuators can provide cost effective means to        significantly increase munitions precision and thereby the        probability of a hit.    -   14. The disclosed actuators can be used in both subsonic and        supersonic projectiles.

The disclosed actuators have a wide range of military and commercialapplications, particularly when powered pneumatically and evenhydraulically, as mechanical stepper motors with position lockingcapability.

The disclosed “mechanical stepper motor” type actuators and their basicoperation and methods of their design and manufacture and integrationinto the structure of projectiles will now be described in detail bylinear mechanical stepper motor design shown in FIGS. 1 a and 1 b. It isshown that the disclosed actuators would provide very cost effective andhave high actuation force/torque and dynamic response characteristics,while occupying very small useful projectile volume and requiring verylow electrical power. It is also shown that the disclosed actuators canbe capable of being readily scaled to the desired application. Thedisclosed actuator concepts could be built as modular units and couldform the basis for developing a common actuator solution for anygun-fired projectile, mortar or missile.

In addition, different methods of powering and driving the disclosedactuation devices are described.

Furthermore, methods of obtaining multistep actuation devices with oneor more coarse and fine step sizes to achieve the desired speed andpositioning precision are described.

An overall view of the basic linear mechanical stepper motor type linearactuator 10 is shown in FIG. 1 a. The cutaway view of the actuator 10showing its internal components is shown in FIG. 1 b. The linearmechanical stepper motor 10, FIG. 1 a, hereinafter also referred tosimply as a linear motor, a linear actuator or a linear stepper motor,consists of two major parts, a body 11 (the stationary part of thelinear motor) and a shuttle 12 (the linearly translating part of thelinear motor). In the munitions applications, the body of the linearmotor is preferably an integral part of the projectile structure as aload-bearing structure of the projectile, thereby allowing the linearmotor to occupy minimal internal volume.

The cutaway view of the linear motor 10 is shown in FIG. 1 b. Theshuttle 12 is seen to be provided with equally spaced pockets 18 facingdownward towards the base of the linear motor 10. The shuttle 18 isprovided with a guide 20 for its linear translation inside the linearmotor body 11. Within the linear motor body 11 are also provided with atleast three equally spaced detonation activated actuator “pins” 13. Theactuator pins 13 are provided with matching guides 14 in the actuatorbody 11 within which they could translate. In the design shown in FIGS.1 a and 1 b, the actuator pins 13 are biased downward by return tensilesprings 15 as shown in FIG. 1 b, positioning them normally in adisengaged position with respect to the shuttle pockets 18 as seen inFIG. 1 b.

In the design shown in FIGS. 1 a and 1 b, a number of layers ofdenotation charges 17 are provided in a space 16 under the actuator pins13. The layers of detonation charges 17 may be detonated electronically(not shown) in a sequential manner by the actuator controller unit (notshown). The detonation and timing of detonation charges and theelectronics therefore are well known in the art. The basic operation ofthe high force/torque and high dynamic response mechanical linearstepper motor 10 is described below.

The operation of the disclosed class of mechanical linear stepper motorlike actuator 10 is best described by the schematic of FIG. 2, which isin effect the frontal cutaway view of the basic components of the linearactuator 10 shown in FIGS. 1 a and 1 b. The operation of this class ofstepper motor like actuators is based on the principles of operation ofsimple Verniers. A Vernier (also called a Vernier scale) is “A small,movable auxiliary graduated scale attached parallel to a main graduatedscale, calibrated to indicate fractional parts of the subdivisions ofthe larger scale, and used on certain precision instruments to increaseaccuracy in measurement” (The Free Dictionary by Farlex, Inc., 1051County Line Road Suite 100, Huntingdon Valley, Pa. 19006).

In the linear mechanical stepper (motor) actuator 10, the shuttle 12 ofthe actuator is provided with pockets 18 (numbered 1 through 7 in FIG.2) that are positioned a distance D apart as is shown in FIG. 2. Threeactuating pins 13 (indicated with letters A, B and C) are sized toclosely fit the shuttle pockets 18, can translate in the guides 14provided in the actuator body 11, and are positioned a distance d apartwhere d>D. Letd−D=δ  (1)

Now consider the situation in which the actuator pin C has been pushedinto the pocket 6, thereby lining up the shuttle 12 above the actuatorbody 11, followed by the withdrawal of the pin C, as can be seen in FIG.2. Now by pushing the actuator pin B up into the pocket 4 as shown inFIG. 3 a, the pocket 4 is then lined up with the actuator pin B, therebyadvancing the actuator shuttle 12 one step to the right. To advance theactuator shuttle 12 one more step to the right, the actuator pin A ispushed up into the pocket 2 of the actuator shuttle 12 as shown in FIG.3 b and then retracted. At this point, the actuator pin C may be pushedinto the actuator pocket 5 as shown in FIG. 3 c and then retracted,thereby moving the actuator shuttle 12 one more step to the right. Atthis point, the shuttle 12 pockets 18 are in a similar position over theactuator pins as they were initially as shown in FIG. 2, with thedifference of having been advanced one full pocket distance D to theright. By repeating the above sequence of pin A, B and C actuation, theactuator shuttle 12 can be moved further steps to the right. The pins A,B and C are pushed into the pockets by detonation of one or more of thedetonation charges 17.

The actuator shuttle 12 may be moved similarly a desired number of stepsto the left, starting from any one of the shuttle 12 positions shown inFIG. 2 or 3. For example, starting from the shuttle 12 position shown inFIG. 2, the shuttle is moved one step to the left by actuating the pin Ainto the pocket 3. The second step to the left is then achieved byactuating the pin B into the pocket 5. The next step to the left is thenachieved by actuating the pin C into the pocket 7.

It is noted that in the linear actuator 10, the upward motion of theactuator 10 pins 13 is shown to be achieved by the detonation of onelayer of the charges 17 provided in the space 16 under the selectedactuator 10 pins 13, followed by the discharge of the pressurized gasesin the compartment 21 under each actuator 10 pin 13 and the pulling backof the actuator 10 pin 13 by the provided tensile spring element 15.This may be readily achieved by the provision of exhaust vents (shownfor example in FIG. 3 b corresponding to only pin B but which would beused for each of the pins) that are positioned such that in theirresting position, the pins 13 cover the vent hole(s) 23. Then onceactuated, the pins 13 pass the vent hole(s), thereby allowing thegenerated pressurized gases to substantially escape through the venthole(s) 23, thereby allowing the tensile return springs to return thepin to its resting position.

In FIGS. 1-3, the disclosed method of developing mechanical steppermotors is presented for the case of a linear stepper actuator (motor).It is, however, appreciated by those skilled in the art that thedisclosed method can be readily used to design rotary mechanical steppertype actuators (motors) with partial or full range of rotations such asthe rotary actuator 30 shown in FIGS. 4 a-4 c. The rotary stepper motortype mechanical actuator 30 is designed to provide full rotary motion.The rotary actuator 30 consists of a circular body 31 with providedcircularly positioned guide 32 with circularly shaped shuttle 33 to rideinside the guide 32 as shown in FIGS. 4 a-4 c.

It is readily seen that by varying the distance d (FIG. 2) and therebythe difference δ, equation (1), the step size of the present mechanicallinear actuator 10 can be varied. In a similar manner, as is expectedfrom the present Vernier-based stepper motor like linear actuator 10,more than three actuation pins 13 and larger or smaller differences δmay be used to achieve almost any stepper motor step size.

In a second embodiment, more than one set of actuation pins 13 can beprovided which operate independent of each other and may be positionedin line or parallel to each other, i.e., one set behind the other, toachieve two or more step sizes to, for example, course step and finestep sizes. In such a configuration, a shuttle 12 may be providedcorresponding to each set of pins 13 or a single shuttle 12 may be usedhaving two sets of pockets 18 (one corresponding to each of the sets ofpins 13).

In addition, for the same body 11 and a shuttle 12 with different pocketdistance D, the step size is readily varied within a certain limitindicated by the size of the pin 13 angled tips 22, FIG. 2, which wouldstill allow sequential operation of the pins 13.

Alternatively, a modular actuation pin portion that is shown embedded inthe body 11 of the actuator 10, FIGS. 1-3, may be constructed separatelyand be attached to the actuator body 10 with the same positioningrelative to the guide 20 to similarly actuate the shuttle 12. In such adesign, by selecting actuator portions with different pin spacing d, thestep size of the linear motor is similarly varied.

Alternatively, each actuating pin assembly may be constructed separatelyand then attached to the actuator 10 body 11 with a desired pin spacingd, to achieve the desired step size for the linear stepper (motor)actuator 10.

Alternatively, it is readily observed that the body 11 of the presentmechanical linear stepper (motors) actuators 10 can be an integral partof the structure of the projectile as a load bearing component. As such,one only needs to machine the guide 20 for the aforementioned shuttle12, position the shuttle 12 in place and attach a modular actuator pinunit in place to complete the assembly of the mechanical components ofthe actuator into the structure of the projectile.

Alternatively, the guide 20 may be a separate modular component that isattached to the body of the projectile, for example, via fasteners suchas screws. The pin assembly or individual pin assemblies may then beattached separately to the body of the projectile to achieve the desiredshuttle 12 motion.

It is also appreciated by those skilled in the art that the maximum stepsize of the disclosed stepper motor like actuators is dependent andlimited by the width of the actuating pin 13 tip 22 (base diameter ofthe pin 13 tip 22 cone if a conical tip 22 is used).

It is also appreciated by those skilled in the art that with any sizewidth of the actuating pin 13 tip 22 (or based diameter of the pin 13tip 22 cone if a conical tip 22 is used), any desired pin spacing d,thereby any desired step size δ may be achieved, FIG. 2. However, whenthe width of the actuating pin 13 tip 22 (or based diameter of the pin13 tip 22 cone if a conical tip 22 is used) is relatively larger and thedesired pin spacing d is relatively small such that the pins may overlapeach other if are positioned side by side in a single plane, then thepins have to be positioned back and forth enough to clear each other,for example the pin B in FIG. 2 may be positioned in the back (or in thefront) (i.e., further in or out of the page) of the pins A and C toallow for larger actuating pin 13 tip 22 to be positioned between thepins A and C. The width of the shuttle 12 must then be appropriatelyincreased to allow for the required number of rows of pockets 18 (in theexample two rows of pockets 18) to be provided in the shuttle 12.

It is noted that the above description of the design and operation ofthe stepper motor like linear actuator (motor) is provided mainly withthe objective of describing the method of design and basic principles ofoperation of the disclosed “mechanical stepper motors”. In the followingpart of the present disclosure, other embodiments of the disclosed“mechanical stepper motors” and their different possible implementationsand operational characteristics are described.

Also, more than one row of pockets 18 may be provided on the shuttle 12with a corresponding set of pins 13 provided for each row. For example,two such rows of pockets 18 can be provided in the shuttle 12 with twosets of pins 13. The width of the actuating pins 13 tip 22 and/or pinspacing d, can be varied between sets of pins/pockets to have adifferent step size δ for each set of pins. In this way, one of the setsof pins/pockets can be used to step the shuttle in a coarse adjustmentand the other set of pins/pockets can be used to step the shuttle in afine adjustment.

The overall view of such a rotary mechanical stepper motor (actuator) 30is shown in FIG. 4 a, with a cutaway view shown in FIG. 4 b, a close-upview of which is shown in FIG. 4 c. As can be observed, in such aconfiguration, the actuation pins 34 are still positioned inside thebody 31, but along a circular arc 35, above which the shuttle 33 pockets36 are positioned. The upward motion of the actuator 30 pins 34 is shownto be achieved by the detonation of one or more layers of the charges 37provided in the space 38 under the selected actuator 30 pins 34,followed by the discharge of the pressurized gases and the pulling backof the actuator 30 pins 34 by the provided tensile spring element 39 aswas previously described for the linear mechanical stepper motor(actuator) shown in FIGS. 1 and 2. The clockwise and counterclockwiserotation of the shuttle 33 is achieved in an identical manner by thesequential actuation of the actuating pins 34.

It is appreciated by those familiar with the art that the mechanicalrotary stepper motor (actuator) shown in FIGS. 3 a-3 c may be fabricatedfor either full rotary actuation; as a circular arc to produce a desired(limited) range of angular rotation; or displacing a shuttle along adesired arbitrarily curved path.

It is also appreciated by those familiar with the art that all theaforementioned variations in the construction of the mechanical linearstepper motors (actuators), FIGS. 1-3, can be readily implemented on theabove mechanical rotary stepper motors (actuators) shown in FIGS. 4 a-4c.

It is noted that in the aforementioned linear and rotary mechanicalstepper motor like actuators, the actuating pins 13 and 34, FIG. 1 b andFIGS. 4 b-4 c, respectively, are integrated into (or the actuating pinassemblies are attached to) the body of the actuators. Here, the bodies11 and 31 of the actuators, FIGS. 1 a and 4 a, respectively, areattached to the structure of the projectile (i.e., grounded or fixed),while the shuttles 12 and 16, FIGS. 1 a and 4 a, respectively, aremoving relative to the bodies 11 and 31. It is, however, appreciated bythose familiar with the art that alternatively, the actuating pins 13and 34, FIG. 1 b and FIGS. 4 b-4 c, respectively, may be integrated into(or the actuating pin assemblies be attached to) the body of theshuttles 12 and 16, FIGS. 1 a and 4 a, respectively. The pockets 18 and36, FIGS. 1 b and 4 c, respectively, are then provided in the body ofthe actuators 10 and 30, FIGS. 1 and 4, respectively.

In the above embodiments, the actuators of FIGS. 1 and 4, the actuatorpins 13 and 34, FIG. 1 b and FIGS. 4 b-4 c, respectively, are shown tobe biased by the provided tensile springs 15 and 39, respectively, tonormally stay in their “pulled back” (disengaged from the shuttle)position. The upward motion of the actuator pins 13 and 34 are thenachieved by the detonation of one layer of the charges provided underthe actuator pins. The pressurized gases in the compartment under eachactuator pin that drive the pin upward to engage the shuttle and causeit to move one step to the right or to the left is then discharged,thereby causing the actuator pin to be pulled back by the providedtensile spring element. The discharging of the pressurized gas may beachieved by the provision of exhaust vents 23 that are positioned suchthat in their resting position, the pins sealingly cover the venthole(s) 23. Then once actuated, the pins pass the vent hole(s), therebyallowing the generated pressurized gases to substantially escape throughthe vent hole(s), thereby allowing the tensile return springs to returnthe pin to its resting position.

This method of venting the pressurized gases is very simple and does notrequire provision of directional valves of any kind. The resultingactuation system will also be very small and more reliable since it doesnot require additional components. The system will also not requireexternal power to actively actuate switching valves.

In the above mode of operation, the actuation devices (linear and/orrotary) do not lock the shuttle to the actuator body, i.e., once theshuttle has moved a step to the right or to the left, since theactuating pin is retracted, the shuttle is held in place only byfriction forces and by any external forces that tend to keep it in itsnew position. This would mean that if external forces are acting on theactuator, then the shuttle (rotor) may be pushed away from its newposition. The system designer would then have the following two optionsfor minimizing or eliminating the resulting positioning errors.

The first option is to provide an external brake to lock the shuttle tothe actuator body. This is what is commonly done with electrical stepper(or other similar type) motors used to move an object to a specifiedposition and keep the object in that position such as electric motorsused in positioning stages, robotic arms and the like. This is generallydone so that external power would not be required to keep the device inits prescribed position while external forces, including gravitationalforces, are acting on the system. The braking of the motor, i.e.,locking the device in its prescribed position, would also add topositioning accuracy of the system since external disturbances would notcause the device to be displaced from its prescribed position.

The second option is to use a servo (feedback) control system tocontinuously tend to move the shuttle closer to its prescribed positionas external disturbances cause the shuttle to be displaced away from itsprescribed position. Such an option is also commonly used in the art forvarious electrical and other types of linear and rotary actuationdevices. However, when the shuttle (device being driven) is at times tobe held in a prescribed position, this option would demand aconsiderable amount of power to operate. The latter energy that isconsumed by the motor (actuator) does not amount to any useful worksince in effect it is used to generate reaction forces that could haveotherwise been generated by a braking device that would require arelatively small amount of electrical energy to actuate. The lockingtype actuation devices, if appropriate for the application at hand, aregenerally preferable since they lead to much simpler guidance andcontrol systems.

The added advantage of the disclosed linear and rotary actuation devicesis that they could be readily configured to operate as stepper motorswith integral locking mechanisms. This is readily accomplished asfollows.

Consider the disclosed linear mechanical stepper motor like actuator 10shown in FIGS. 1-3. In this embodiment, the actuating pins 13 are biaseddownward by the tensile springs 15. As a result, following eachactuation action, i.e., after an actuating pin 13 is pushed upward intothe provided shuttle pocket 18, the return tensile spring 15 pulls thepin back into its rest position once the pressurized gases in thecompartment 16 have been substantially vented through the providedventing holes (23) as described previously. The provision of the tensilereturn springs 15 actually allows the actuating pin 13 to act similar toa single acting pneumatic piston. The disclosed actuation devices 10 and30, FIGS. 1 and 4, respectively, can however be transformed to steppermotor like actuation devices with integral position locking featureswith minimal modification. This is accomplished using either one of thefollowing methods:

In the first method, the aforementioned tensile return springs 15 areremoved and the actuating pins 13 are provided with the means to operateas a double acting pneumatic piston. In this embodiment 40, theactuating pins shown in FIG. 5 a are replaced with actuating pins 41 asshown in FIG. 5 b. Such actuating pins 41 can be designed with a piston42 with a space 43 provided in the piston front as shown in FIG. 5 b. Inthis embodiment, the detonation charges 45 provide the pressure to forcethe actuating pins 31 up to actuate the shuttle 12 to the right or tothe left. No tensile return springs are provided. In addition, no ventsare provided to discharge the pressurized gas. The pressurized gas wouldthen keep the shuttle 41 locked to the actuator 40 body 11.

It is noted that as shown in FIGS. 1-3, the straight portion of theactuating pins 13 below their angled tips 22 fits inside the shuttlepocket 18, providing the means to resist further movement of the shuttle12 relative to the actuator body 11, i.e., locking the shuttle 12 to theactuator body 11. In the embodiment 40 of FIG. 5, the actuating pin 41is also provided with a straight portion 46 (cylindrical if the pin iscylindrical) so that when actuated, the straight portion 46 fits insiderthe shuttle pockets 47, thereby locking the shuttle 12 to the actuatorbody 11. The one actuated pin 41 is then retracted following thedetonation of charges in a second pin chamber 44, which would alsoactuate and open a vent to allow the pressurized gases to escape fromthe first pin chamber 44, and pressurizing its frontal space 43 to forcethe first actuating pin 41 down into its rest position. This wouldeffectively provide the means to allow the actuating pins 41 to act asdouble acting pneumatic cylinders. Such pneumatic valve systems toaffect such pressurized gas routing are well known in the art and arenot shown in FIGS. 5 a and 5 b.

In the second method, the tensile return springs 15, FIGS. 1-3, areretained. The pressurized gas vent holes 23 described for theembodiments of FIGS. 1-3 are, however, removed. As previously described,the detonation charges 17 will provide the force to push the actuatingpins 13 up to actuate the shuttle 12 to the right or to the left. Sinceno vents are provided to discharge the pressurized gas, the pressurizedgas would keep the shuttle 12 locked to the actuator body 11. Theactuated pin 13 is then refracted following the detonation of charges 17in the chamber 16 of a second actuating pin 13, which would actuate thesaid second actuating pin 13, and which would also actuate and open avent to allow the pressurized gases to escape from the first actuatedpin 13 chamber 16. The tensile return spring 15 will then retract thefirst actuating pin 13 to its rest position, thereby allowing the secondactuating pin 13 to actuate the shuttle 12 to the right or to the left.This would effectively provide the means to allow the actuating pins 13to act as single acting pneumatic cylinders with spring returnmechanisms 15.

The latter embodiment constructed using the above second method can besimpler in design and does not require more complex valves to actuatethe former double acting pin version design.

It is appreciated by those skilled in the art that the above shuttle 12position locking feature (constructed using either one of theaforementioned methods) can be readily extended to rotary actuationdevices (such as the one shown in FIG. 4) and even to actuating devicesthat provide almost any arbitrarily curved motions.

In the embodiments of the FIGS. 1-5, the pressurized gas used to actuatethe actuating pins (13, 34 and 41 in FIGS. 1, 4 and 5, respectively) aregenerated by the detonation of charges that are stacked in the cavitybelow the actuating pins. In these embodiments, a number of individualcharges (17, 37 and 45 in FIGS. 1, 4 and 5, respectively) are packedwithin the cavity and detonated on command to generate the requiredpressure within the cavity to actuate the actuating pins. This method ofgenerating the actuation gas pressure is hereinafter referred to as“direct charge detonation method” or “direct method of pressuregeneration” inside a pin cavity to affect actuation.

The aforementioned actuating pressurized gases may, however, begenerated within one or more separate “reservoirs” and then be routedvia (e.g., pneumatic) valves to actuate the individual actuating pinsupon command. The “reservoir” preferably accommodates enough pressurizedgas to actuate the pins a number of times. This method of generating thepressurized actuation gases for operating the said actuating pins ishereinafter referred to as “indirect charge detonation method” or“indirect method of pressure generation”.

The aforementioned direct and indirect methods of generating pressurizedgases for the operation of the actuating pins each has certain meritsand shortcomings, generally depending on the selected application. Thefollowing is a short list of potential advantages and disadvantages ofeach one of the above methods, particularly for munitions applications.

The following is a number of potential advantages and disadvantages ofthe aforementioned direct method of pressure generation for theoperation of the said actuating pins as compared to the aforementionedindirect method of pressure generation:

-   -   For munitions applications or in devices used for emergency use        in which the number of steps that the actuator has to move        during its entire actuation cycle is rather limited, the direct        method of actuation pressure generation is usually more suitable        since it would lead to a less complex device and it would occupy        less volume. In addition, the resulting actuators do not require        actuation valves for their operation.    -   The direct method has the advantage of not requiring a pressure        reservoir, which would occupy certain amount of volume depending        on the number of steps is desired to be provided in between        “charging” of the reservoir via detonation of individual        charges.    -   The direct method has the advantage of being able to provide        very high localized pressure, thereby being capable of providing        very high pin actuation forces and as a result, very high        actuation forces and torques.    -   One disadvantage of the direct method is that since the required        direction of actuation (to the right or left for linear and        clockwise or counterclockwise for rotary actuators) are not        known a priori, therefore the pin cavities have to be stacked        with a significantly larger number of detonation charges that        might be needed to ensure their availability during any        operational scenario.

The following is a number of potential advantages and disadvantages ofthe indirect method of pressure generation for the operation of the saidactuating pins as compared to the aforementioned direct method ofpressure generation:

-   -   The main advantage of the indirect method is that the        pressurized gases used to operate the actuating pins are        generated in one or more reservoir and then distributed to the        acting pin. In this method, the space required to house        detonation charges for each individual pin and their initiation        devices and wiring are eliminated. Fewer detonation charges        providing relatively larger volumes of pressurized gas can be        used to power several actuation steps at a time.    -   The actuator using this method requires pneumatic valves to        route the pressurized gases to individual actuating pins. These        valves can, however, be one-way pneumatic valves, which can be        very simple and very low power to operate.    -   The potential disadvantage of indirect method is that it may        lead to a slightly larger overall volume than direct method        based actuation devices. In addition, the actuating gas pressure        will generally be lower than those possible with the direct        method. However, the additional volume can be minimized by also        integrating the reservoir into the structure of the projectile.

FIG. 6 a illustrates the overall view of a typical linear actuatorembodiment 50 operating based on the aforementioned “indirect chargedetonation method” or “indirect method of pressure generation”. Thecutaway view of the actuator embodiment 50 showing the internalcomponents of the actuator is shown in FIG. 6 b. In this embodiment, theactuating pressurized gases are generated within at least one“reservoir” unit 51 and are then routed via control valve unit 52 toactuate the individual actuating pins upon command to the individualactuating pin 53 valves 57 as previously described. The at least one“reservoir” unit 51 can accommodate enough pressurized gas to actuatethe actuating pins 53 a number of times.

In the embodiment 50 of FIGS. 6 a and 6 b, the reservoir unit 51consists of a pressurized gas reservoir 54 and at least one (single orstack of several individually detonated) pressurized gas generatingdetonation charges 55 and the shuttle 59. In this embodiment, when thepressure in the gas reservoir 54 drops below a specified level, one ofthe separate charges 55 (a total of 39 such individual detonationcharges are shown in FIG. 6 b) is initiated to replenish the reservoir54. This allows the linear mechanical stepper motor like actuator 50 tooperate with much higher efficiency because the constraint of chargeallocation in a given cylinder in actuators using the aforementioneddirect method of pressurized gas generation, FIGS. 1-5, is removed. Sucha design could obviously accommodate significantly larger number ofcharges and allow a significantly number of actuation steps.Additionally, optimization of the design based on the parameters ofreservoir 54 volume, volume occupied by the detonation charges 55,reservoir pressure, and the desired actuating pin 53 operating pressurewill yield very high compactness for the device.

The actuating pins 53 may be single acting with tensile return springs58 as shown in FIG. 6 b, or may be double acting as described for theembodiment of FIG. 5 b. In either case, by a proper sequence ofoperation of an actuating pin 53 valve 57, the shuttle 59 may or may notbe locked to the body 56 of the actuator 50 as previously described.

In the embodiment 50 shown in FIGS. 6 a-6 b, the actuator body 56 andthe pressurized gas reservoir 54 are can be integral and/or load bearingparts of the projectile structure. The pressurized gas chamber may bepositioned as shown in FIGS. 6 a and 6 b, or positioned in any otherposition and direction to accommodate the design of the projectilestructure.

FIG. 7 a illustrates an overall view of another embodiment 60. FIG. 7 bshows a cutaway view of the embodiment 60 showing the internalcomponents of the mechanical stepper motor like linear actuation device.The actuator embodiment 60 is similar in construction and operation tothe mechanical stepper motor like linear actuator with double actingactuation pins shown in FIG. 5, with the main difference being thepositioning and method of storing the actuating detonation charges. Theactuator 60 has an actuator body 61 and a shuttle 62 with shuttlepockets 63, FIGS. 7 a and 7 b. The actuator body 61 is provided with atleast one “driving charge” chamber 64 and at least one “return charge”chamber 65 within each of which at least one detonation charge 68 isprovided, FIG. 7 b.

The linear actuator 60 is constructed with at least three double actingactuating pins 69 (cylinders), with both actions powered by detonationof the indicated charges, one driving charges 68 in at least one chamber64 to drive the actuation pin 69 to actuate the shuttle 62, and onereturn charges 68 in at least one chamber 65 to retract the actuatingpin 69 away from the shuttle 62 as shown in FIG. 7 b. The actuating pins62 are provided with the piston 67 to allow the pressurize gasesgenerated by charges in the at least one chamber 64 to push theactuating pin 69 forward to engage the shuttle 62 pockets 63 and drivethe shuttle 62 to the right or to the left. The actuating pins 62 arealso provided with a smaller sized middle portion 71 to allow theformation of a chamber 70, thereby allowing the pressurize gasesgenerated by charges in the at least one chamber 65 to push theactuating pin 69 back to engages the shuttle 62 pockets 63.

It is appreciated by those skilled in the art that the aforementioned“driving charge” and “return charge” chambers may be positioned as shownin FIG. 7 b, or be positioned in any other direction to accommodate thedesign of the projectile structure. Such a design could obviouslyaccommodate significantly larger number of charges for a given length ofthe actuating pin 66 assembly.

It is appreciated by those familiar with the art that the linearmechanical stepper motor like actuator shown in FIGS. 7 a and 7 b mayalso be constructed as a rotary actuator similar to that shown in FIG.4, and in fact as a mechanical stepper motor like actuator providing anarbitrarily curved motion.

In the embodiments shown in FIGS. 1-5, the gas pressure used to displacethe actuation pins were shown to be generated by the detonation ofcharges that are stacked in the cavity below the actuating pins. In thisdesign, a number of individual charges are packed within the said cavityand detonated on command to generate the required pressure within thecavity to actuate the actuating pin.

In alternative embodiments, the stacked (or individual) charges may bepositioned outside the actuation pin chamber as shown for the at leastone “driving charge” chamber 64 housing the detonation charges 68 in theembodiment 60 shown in FIG. 7 b. The generated pressure is thenchanneled directly (as shown in FIG. 7 b) or through provided passagesto actuate the actuating pins. The main advantage of such a detonationcharge storage arrangement is that it would allow a significantly largernumber of detonation charges to be provided without making the actuationpin assemblies very long.

The embodiments shown in the FIGS. 1-7 are actuated by pressurized gasesgenerated by detonation charges. Such actuation devices are particularlyappropriate for applications in gun-fired projectiles, mortars, missilesand other applications in which the actuator is required to operate fora limited and relatively short period of time, and also when very highactuating forces/torques are to be generated by direct detonation ofindicated charges.

Alternatively, pressurized gas (such as air) or fluid (such as hydraulicfluids) may be provided from external sources and used to drive thedisclosed linear and rotary mechanical stepper motor like actuationdevices such as those shown in FIGS. 1-7. As an example, the embodiment50 shown in FIGS. 6 a and 6 b is redrawn as the linear mechanicalstepper motor like actuator 80 in FIG. 8, with the reservoir unitreplaced with at a simple pneumatic inlet 81 through which pressurizedgas (such as air) is supplied for the actuation of its actuating pins.The remaining components of the actuator embodiment 80 are the same asthose of the embodiment 50 shown in FIGS. 6 a and 6 b. The pressurizedgas operating this actuator can be air and can be provided by anexternal source (not shown). The main advantage of this mechanicalstepper motor like actuator is that it could be operated without anynumber of step limitations.

It is appreciated by those familiar with the art that all the linear androtary mechanical stepper motor like actuators described in thisdisclosure, including those shown in FIGS. 1-7, may be similarlydesigned to operate pneumatically with pressurized air (or other gases).Such pneumatic mechanical stepper motor like actuators are best suitedfor applications in which they are to be operated for relatively longperiods of time. The resulting pneumatic mechanical stepper motors likeactuators are more suitable for non-munitions applications, particularlyfor production type machinery. The resulting pneumatic actuators may beoperated as previously described with or without step position lockingfeature. The mechanical stepper motors described herein can also operatewithout actuation by pressurized gas (other means for actuation), suchas by hydraulic actuation of the pins. Hydraulic activation is wellknown in the art, such as in hydraulic actuator cylinders.

It is noted that the aforementioned pneumatic linear and rotarymechanical stepper motor like actuators may operate with theaforementioned single-acting (spring return) or double-acting actuationpins. In certain applications, such as when high external dynamic forcesare experienced by the actuation device, double-acting actuating pinsand/or step position locking features may be required to achievenecessary performance. The additional logic and plumbing for adouble-acting and/or step position locking designs is well known in theart, and the overall compactness of the device will not changedramatically.

Referring now to FIGS. 9 a-9 b, there is shown an exemplaryconfiguration of a mechanical stepper motor integrated into thestructure of a projectile 90. In the exemplary configuration of FIGS. 9a-9 c, the mechanical stepper motor is of a rotary configuration, suchas that shown and described with regard to FIGS. 4 a-4 c (referred towith reference numeral 30) and the same is used to control a controlsurface of the projectile 90, which in the exemplary configuration ofFIGS. 9 a-9 c is a canard 92. The guide 32 of the rotary mechanicalstepper motor is integrated into one of the nose cone 94 or body 94 ofthe projectile 90 and the shuttle 33 is allowed to freely rotate withinthe nose cone 94. A portion of the shuttle 33 carries a geared surface98 which is provided to mesh with a rotatable gear 100. The canard 92includes a shaft 102 connected to the gear 100. Thus, rotation of theshuttle 33 in turn rotates the gear 100 which in turn rotates the canard92 to control the projectile as desired.

Although shown with regard to varying a control angle of a canard 92,the disclosed mechanical stepper motors, linear and/or rotary, can beused to control other features of projectiles, deploy features fromprojectiles (e.g., wings or other control surfaces) and/or vary an outersurface shape and/or dimension of the projectile (see e.g., U.S. Pat.Nos. 6,727,485; 6,923,123; 6,982,402; 6,935,242 and 7,150,232; thecontents of each of which are incorporated herein by reference).

As discussed above, the mechanical stepper motors disclosed herein canbe stacked in parallel (e.g., two linear mechanical stepper motorsstacked in parallel, one or which for a coarse adjustment and one for afine adjustment; two linear mechanical stepper motors placed orthogonalto each other to create and X-Y table; three linear mechanical steppermotors each placed orthogonal to another to create an X-Y-Z table; one,two or three linear mechanical stepper motors as described immediatelyabove having a rotary mechanical stepper motor at one or all of the X, Yor Z axes) and/or in series (any combination of linear and/or rotarymechanical stepper motors placed in series so as to customize for anyconceivable complex motion).

Lastly, although in the embodiments in which the pin is biased, it isbiased on the unengaged position, the pin can also be biased in theengaged (locked) position and the charge (or other activation means) canbe used to disengage the pins. Furthermore, some pins can be in thenormally engaged position and disengaged with a charge (or otheractivation means) to free the carriage at which point other normallydisengaged pins are engaged with a charge (or other activation means) tochange the position of the carriage, at which point the normally engagedpins can re-engage (e.g., pressure vented) to lock the carriage in thenew position.

The mechanical stepper motors and actuators disclosed above havewidespread commercial use in robotics and automated manufacturing ingeneral and in semiconductor manufacturing in particular. Assemiconductor devices become increasing complex and the density ofcomponents contained on semiconductors increases, there is an urgentneed for precise control of the automated equipment for manufacturingthe semiconductor wafers. The proposed novel mechanical stepper motorsand actuators can provide such precise control. For example, during themask-making process of a semiconductor wafer, the mechanical steppermotors and actuators can be used to precisely drive a laser or electronbeam to selectively remove chromium and create the mask.

The mechanical stepper motors and actuators disclosed above also havewidespread commercial use where sanitary conditions are necessary, suchas in the food industry. Because the mechanical stepper motors andactuators disclosed above do not require electrical coils (as doelectric stepper motors), they can be washed down to meet FDA standardsfor certain food manufacturing processes.

The mechanical stepper motors and actuators disclosed above also havewidespread commercial use in emergency situations that may require alarge generated force and where a one time use may be tolerated. ForExample, the mechanical stepper motors and actuators disclosed above canbe configured to pry open a car door after an accident to free a trappedpassenger or pry open a locked door during a fire to free a trappedoccupant. By using a large explosive force, the novel mechanical steppermotors and actuators disclosed above can generate a very large force andthe one time use of the device can be tolerated in emergency situations.

While there has been shown and described what is considered to bepreferred embodiments of the invention, it will, of course, beunderstood that various modifications and changes in form or detailcould readily be made without departing from the spirit of theinvention. It is therefore intended that the invention be not limited tothe exact forms described and illustrated, but should be constructed tocover all modifications that may fall within the scope of the appendedclaims.

1. A mechanical stepper motor comprising: a shuttle having one of aplurality of pockets and movable pins offset from each other with afirst spacing; a body portion having the other of the plurality ofpockets and movable pins offset from each other with a second spacing,where the first spacing is different from the second spacing; andactuation means for engaging at least one of the movable pins into acorresponding pocket to step one of the shuttle and body portion apredetermined linear and/or rotary displacement.
 2. The mechanicalstepper motor of claim 1, wherein the predetermined displacement islinear.
 3. The mechanical stepper motor of claim 2, wherein the bodyportion comprises a shuttle guide for movably holding the shuttle andpin guides for movably holding the pins.
 4. The mechanical stepper motorof claim 1, wherein the predetermined displacement is rotary.
 5. Themechanical stepper motor of claim 4, wherein body portion comprises pinguides for movably holding the pins and the shuttle is rotatablydisposed on the body portion and comprises the pockets.
 6. Themechanical stepper motor of claim 1, wherein the activation meanscomprises one or more detonation charges for producing a pressurized gasacting on at least one of the pins to one of engage and disengage thepins with a pocket.
 7. The mechanical stepper motor of claim 6, furthercomprising a biasing means for biasing the at least one pin in adisengaged position, wherein the activation means further comprises avent hole for releasing the pressurized gas from acting on the pin andallowing the biasing means to disengage the at least one pin from thepocket.
 8. The mechanical stepper motor of claim 6, wherein the one ormore detonation charges are provided in a space in direct communicationwith a portion of the at least one pin.
 9. The mechanical stepper motorof claim 6, wherein the one or more detonation charges are provided topressurize a reservoir in fluid communication with a portion of the atleast one pin through one or more valves.
 10. The mechanical steppermotor of claim 1, wherein the activation means comprises one or more ofthe pins having a first portion acted upon by a first pressurized gas toengage the one or more pins and a second portion acted upon a secondpressurized gas to disengage the one or more pins.
 11. The mechanicalstepper motor of claim 10, wherein the first pressurized gas is providedby one or more first detonation charges and the second pressurized gasis provided by one or more second detonation charges.
 12. The mechanicalstepper motor of claim 11, wherein the first and second detonationcharges are disposed in the body.
 13. The mechanical stepper motor ofclaim 1, wherein the activation means comprises a pressurized fluidsource in fluid communication with a portion of the at least one pinthrough one or more valves.
 14. The mechanical stepper motor of claim13, wherein the pressurized fluid source is one of air and hydraulicfluid.
 15. The mechanical stepper motor of claim 1, further comprisinglocking means for locking a position of one of the shuttle and bodyrelative to the other.
 16. A method for stepping a first member relativeto a second member, the method comprising: providing one of the firstand second members with one of a plurality of pockets and movable pinsoffset from each other with a first spacing; providing the other of thefirst and second members with the other of the plurality of pockets andmovable pins offset from each other with a second spacing, where thefirst spacing is different from the second spacing; and engaging atleast one of the movable pins into a corresponding pocket to step one ofthe first and second members a predetermined linear and/or rotarydisplacement.
 17. The method of claim 16, wherein the engaging comprisesproducing pressurized gas acting on at least one of the pins to engagethe pins with at least one of the pockets.
 18. The method of claim 17,further comprising: biasing the at least one pin in a disengagedposition; and releasing the pressurized gas from acting on the pin andallowing the biasing to disengage the at least one pin from the pocket.19. The method of claim 17, wherein pressurized gas is produced in aspace in direct communication with a portion of the at least one pin.20. The method of claim 17, wherein the pressurized gas is produced topressurize a reservoir in fluid communication with a portion of the atleast one pin through one or more valves.
 21. The method of claim 17,wherein the pressurized gas is produced to engage the one or more pinsand to disengage the one or more pins.
 22. The method of claim 16,wherein the engaging comprises providing a pressurized fluid source influid communication with a portion of the at least one pin through oneor more valves.
 23. The method of claim 16, further comprising locking aposition of one of the shuttle and body relative to the other.